Tin; m:vi:i.<H'MKM m LCMNI 



It may be suspected that the other cases of supposed .-n- 

 togastiir proliferation will prove to be susceptible ot a similar 

 explanal ion. 



Although, as I have endeavored to show, the Ctenophora 

 are readily reducible to the general plan of the Actinozoa, yet, 

 considering their many peculiar characters, I think it i.- 

 visable to separate them from the (Jo-rail- </ //</, as a distinct 

 natural order. 



Molt-over, the Physemaria must undoubtedly be placed 

 in this section, which will, therefore, eon>ist of the following 

 natural orders: Phym-um-ria^ Porifera, Hydrozoa, 



SECTION III. I concur in the proposal of Biitsehli ' to es- 

 tablish a group, Nematorhyncha, for the genera Chcetonotus, 

 Echinoderes, and their allies, to which reference is made at p. 

 101. The j/STematorhyneha are divisible into the Gastrotricha J 

 (Chcetonotus, Chcetura, Cephalidium, Ichthydium, Turin mi- 

 la, JSTew/fA/.s-//*, and Dasydites), which are ciliated on the 

 ventral surface of the body, and the Atricha (Echinoderes), 

 which possess no cilia. Blltschli finds two convoluted water- 

 vessels analogous to those of the Rotifera, but apparently 

 not ciliated, in Chcetonotus. 



SECTION IV. Our knowledge of the development of the 

 Hirudinen has received an important addition in the " M6- 

 moire sur le d^veloppement embryog^nique des Hirudin^es," 

 by M. C. Robin ; who, among other important contributions 

 to embryology, has rectified some important errors of Rathke 

 respecting the early stages of the development of Cleps'nn. 

 I have found the description and figure's of the vaiious stages 

 of cleavage, and of the steps by which the hlastoderm is con- 

 verted into the young Clepsine, given in this memoir, to be 

 exceedingly accurate. 



The whole process in Clepsine is very similar to that which 

 has been described in Euaxes by Kowalewsky, 3 and shares 

 with it the remarkable peculiarity that the first-formed por- 

 tion of the blastoderm becomes the haemal region of the body. 



1 " Untersuchungen fiber freilebende Neraatoden und die Gattung Chatono- 

 tu*:" 1 (ZfiMirit't fur >rtM. Z/trt'' . 1 S 7''-. ) 



a See H. Ludwig, " Ueber die OrdnoDg Gastrotru-lin." (Zeittchrift fur wits. 



Zooloffif, 1876.) 



3 " P^mbryoloirische Studien an Wiirmerii und Arthropoden." (" Me"m. de 

 Acad. Imp.' dt- St.-rotersbourg," 1871. ) 



